Centrifugal treatment of substances and mechanism therefor



May 7, 1935. 2,000,521

CENTRIFUGAL TREATMENT OF SUBSTANCES AND MECHANISMTHEREFOR 0. JONES Filed June 15, 1931 INVENTOR AW ATTORNEYS.

Patented May 7, i935 UNITED STATES 2,000,521 ENTmFUGAL TREATMENT OF SUB- STAN CES AND FOR DIECHANISM THERE- Leo D. Jones, Philadelphia, Pa.., 'assignor to The Sharples Specialty Company, Philadelphia, Pa a corporation of Delaware,

Application June 13, 1931, Serial No. 544,083

'3 Claims. .This. invention relates to method of and mech anism for centrifugal treatment of substances.

It relates particularly to the centrifugal treatment of substances which are del eter'iously affected when subjected to temperatures outside of a limited temperature range favorable to such substances. This invention is applicable, for example, in the centrifugal treatment of a culture of living organisms, such as acidophilus bacilli in a suitable medium, to separate the bacilli from the medium in which they are developed by centrifugal force and recover the bacilli thus separated while controlling temperature conditions during the centrifugal treatment, according to difiiculty that has been experienced heretofore in t recovering such bacilli by the use of centrifugal machines, namely, the death of substantial amounts of bacilli during the centrifugal treatment. a

This invention is applicable, for example, in

the recovery of acidophilus bacilli which are grown according to known methods of culture in culture media such as skimmed milk digested with trypsin. According to methods heretofore used the bacilli, after they have reached a favorable point with respect to number and, vitality, are recovered and concentrated by subjecting the bacilli culture to centrifugal force in an ordinary type of centrifugal machine. As a result of passing the culture through a centrifugal machine a putty-like solid deposits on the inner surface of the wall of the centrifugal rotor. In passing approximately 100 gallons of culture of acidophilus bacilli; for example, through a centrifugal machln about 4 pounds of the putty-like solid is depo ited. This putty-like solid comprises principal y precipitated casein and acidophilus ba-" cilli. For commercial distribution, the puttylike mass comprising acidophilus bacilli concentrated form maybe suspended in, a medium favorable to maintaining the bacilli in a live state. Agar,- for example, may be used if it is desired to preserve the material in solid form. Suitable flavors or coatings may also be employed. 1

The cultures of acidophilus bacilli in suitable media are developed, according to accepted practice, at a temperature corresponding to the normal temperature of the human body. In subjecting the cultures to centrifugal treatment, the cultures are introduced into the centrifugal machine at the same temperature. Upon the pas- 5 Sage of the culture through the centrifugal machine, the culture is heated somewhat so that the efiluent of culture medium from which the acidophilus bacilli have. been separated by centrifugal force is discharged at a temperature about 2 F. higher than the temperature at which the culture was introduced into the centrifugal machine. I have discovered, however, that the the temperature of the human body, e. g. about 98 F., the strata of acidophilus bacilli deposited adjacent the walls of the centrifugal rotor are heated as a result of the centrifugal treatment to temperatures as high as 115 Fahrenheit. I have further discovered that this high temperature which is generated at or adjacent the wall of the centrifugal rotor is responsible for the death of a relatively large portion of the acidophilus bacilli. Experiments which I have made show that this elevation of temperature at or adjacent the wall of'the centrifugal rotor is responsible for the death of about 20% of the acidophilus bacilli contained in a culture of such bacilli which is subjected to centrifugal treatment according to methods heretofore practiced.

It is a feature of this invention that the death of organisms such as acidophilus bacilli from the 40 causeabove described is substantially eliminated to the great improvement of centrifugal methods of concentrating such organisms which have heretofore been practiced. Moreover, while this invention is applicable in improving methods heretofore practiced for centrifugal recovery of living organisms, it is a further feature of this invention that it is applicable also in improving centrifugal treatment of other solid or liquid substances which are adversely affected by temperatures outside of a limited range that is favorable to such substances.

The heat which is developed in subjecting liquids (including liquids containing dispersed liquids and/or'solids) to treatment in a centrifugal machine, I believe to be due in partto the transformation into heat energy of that portion of the mechanical energy applied to the rotor which is consumed in imparting turbulence to liquid and in overcoming friction between the liquid and the rotor parts in bringing the liquid introduced into the rotor up to the speed of the rotor, and in part to the transformation into heat of the kinetic energy of substances discharging from the rotor and being brought to rest. Moreover, as

' the velocity of the material within the'centrifugaltrolling the conditions rotor is proportioned to its distance from the axis of rotation, a greater amount of turbulence and friction occur in bringing up to the speed of the rotor the strata adjacent the wall of the rotor than occur in bringing up to the speed of rotation those strata which are nearer Consequently, the greatest amount of heat is generated in bringing up to the speed of rotation of energy required to overcome resistance to rotation which is afforded by the atmosphere in which the centrifugal rotor is operated. In this case, also, the heat energyv so produced is generated at the wall of the centrifugal rotor.

The amount of heat that is developed in'the centrifugal treatment of substances may be il lustrated as follows: When, for example, aqueous material is introduced into a centrifugal machine at about 98 F. and an aqueous efiluent averaging gallons per hour is discharged at about 100 F., about 833 B. t. u. of heat is generated per hour and is dissipated in the effluent alone. heat is also dissipated into the atmosphere and apparatus about the exterior of the centrifugal rotor. As has been pointed out above, I have found that this heat is-generated for the most part at or adjacent to the wall of the centrifugal rotor so as to cause the temperature of the wall of the rotor to be raised considerably above the I temperature of matter thereabout until sufficient temperature gradient is established to dissipate the generated heat from the wall of the rotor as rapidly as it is developed. Moreovenwhen substances are maintained in contact with the inner surface of the wall of the rotor for any substantial length of time, c. g., as in the case of acidophilus bacilli deposited on the wall of the centrifugal rotor, the dissipation of heat from and through such substances is relatively slow, with the result that heat is held in such substances rather than being rapidly dissipated and that the temperature of such substances is raised considerably above'the temperature of either the material charged to the centrifugal rotor or of the effluent discharged therefrom. In the case of acidophilus bacilli, this heat energy generated in and transmitted to the strata thereof deposited adjacent the wall of the centrifugal rotor is responsible for the death of the organisms hereinabove referred to. According to this invention, a mechanism and method are provided which correct the. un-' desirable heating of the wall of the centrifugal rotor and of substances adjacent thereto by conaboutthe centrifugal rotor .50 as to dissipate the heat energy developed at or adjacent to the wall the axis of rotation.

Additional of the rotor by subjecting substances to centrifugaltreatment, so that the temperature of the rotor wall and of substances adjacent to the rotor wall will not be raised objectionably and so that in the case of acidophilus bacilli, for example, the temperature of the rotor wall and of the bacilli deposited thereon will be maintained at a temperature sufiiciently low to maintain the bacilli in a living condition. Furthermore, the method and means provided according to this invention may also be utilized so as to give favorable difference in temperature between the wall of a centrifugal rotor and liquid passing through the rotor with respect to liquids or solids deposited on the wall of the rotor.

Specific apparatus embodying this invention and which is adapted for the practice of this invention is shown'in the accompanying drawing wherein I Fig. 1 is a centrifugal machine illustrating one embodiment of this invention, comprising a casing adapted to have the temperature of the inner surface thereof modified;

Fig. 2 is another tion, comprising a'jet for discharging liquid or air against the exterior wall of the rotor and/on into the atmosphere immediately surrounding the rotor; r I v Fig. 3 is a further embodiment of this invention, comprising a coil for modifying the temperature of the atmosphereimmediately surrounding the centrifugal rotor. i

In Fig. 1 a centrifugal machine is shown comprising a frame I!) adapted to support rotor-ll from bearing l2 by means of spindle l3 and neck l4. Suitable means for' rotating rotor l I may be employed such as a belt l5 cooperating'with a pulley Iii-fixed to the top of spindle l3 above bearing l2. Disposed about rotor H is a casing H, which is of novel construction according to this invention and which may be supported by frame l0. Covers l8, l9 and 20 rotor II and are adapted to fit into the upper end of easing H. A spout 2| is provided for the chamber formed between covers L8 and I9 and a spout 33 is provided for the chamber between covers l9 and 20. r

Any suitable means of well-known construction not shown for introducing liquids or liquids mixed .with suspended solids into the bottom of the rotor may be employed. An aperture 34 in neck ll of rotor I l is adapted to discharge efiluent from rotor l I. The centrifugal v so-called clarifier type adapted for depositing suspended solids or liquids in the material charged to the rotor on the wall of rotor ll whilepermitting liquid from which-such substances have been separated to be discharged therefrom; The apparatus shown is suitable, for example, in recovering acidophilus bacilli from culture media. 'In such case the bacilli organisms are deposited on the wall of rotor II and the medium therefor from which they have been eparated is discharged from orifice 34. Whil aspeciflc type of rotor and means for charging 5 me with material and discharging eiiiuent ther from is shown, it is to be understood that discontinuous centrifugal treatment of substances may also be used in connection withthis invention and that the type shown has been described for purposes ofillustration merely.

Referring more particularly to the casing I] which in conjunction with a centrifugal rotor comprises novel features and advantages of this invention, this surround the neck of I embodiment of this invenmechanism shown is of the Y oth r types of centrifu- 1 gal rotors adapted for either the continuous or is provided witha double wall, namely, an inner wall 22 and an outer wall 23 so as to leave a space between said walls in which a substance such as water orother liquid or gas may be circulated as by means of inflow and outflow pipes 24 and 25. To increae the surface area of inner wall 22 such surface may be made in the form of corrugations or other deformed shape in the practice of this invention.

In centrifugal mechanism of the above con- .struction, the inner wall 22 of easing I! maybe maintained at such temperature that there will be a gradual interflow of heat between rotor H I and casing wall 22 through the atmosphere there-' between. By controlling the temperature of casing wall 22 the rate of flow ofheat from rotor II chilled to effect a gradual absorption of heat from rotor ii so as to maintain the wall of rotor ii at such temperature that the acidophilus bacilli deposited thereon will be maintained at about the average temperature at which the culture of such bacilli is passed through the rotor and thereby prevent the destruction of such bacilli caused by high temperatures which would otherwise be generated at or adjacent the wall of rotor M and which would be prejudicial to continued maintenance of the acidophilus bacilli deposited on the wall of said rotor in a living state.

In Fig. 2 a construction similar to that of Fig. l is shown, except that in this construction a single walled casing 26 of usual construction may be used. Inside of casing jets or nozzles 2'8- are mounted by any suitable means such as line 28 which passes through casing 255 so as to be supported thereby and which conveys to nozzles 2i substances to be discharged from said nozzles. Nozzles .27! may be adapted to spray a liquid such as water into the atmosphere ediately surrounding rotor i l and/ or may be adapted to spray suchliquid directly on the exterior of rotor ii. When water, for example, is discharged from nozzles 27, the water is adapted to cool the rotor and the atmosphere surrounding the rotor both by elevation of the temperature of the water and by absorption of heat of vaporization as a result of evaporation of the water. 'If about 50 gallons per hour of acidophilus bacilli culture are passed through the centrifugal rotor at about 98 F., a spray of about 20 gallons per hour of water at ordinary atmospheric temperatures has been found to satisfactorily prevent the wall of the centrifugal rotor-from being heated by the centrifugal treatment of the culture to a temperature unfavorable to maintenance of the bacilli in a living state. In addition to water, other liquids maybe discharged from nozzles 2?. For example, it might be desirable in certain cases to discharge liquid carbon dioxide into the atmosphere surrounding rotor ii especially when it is desired to surround the discharged eiiiuent fom the rotor with an inert gas.

In case a liquid is sprayed from nozzles 27 which is not completely evaporated, suitable means such as drain 48 should be provided for permitting the liquid to drain from the bottom of the easing. In addition to discharging liquids from nozzles 21,'air or other gas could be discharged from the nozzles so as to chill the atmosphere surrounding rotor I I. discharged into the atmosphere between .casing 26 and rotor I I any suitable outlet not shown may be employed to permit escape of warmed air or other gas into the atmosphere outside of casing 26.

While it is regarded as preferable to employ a casing 26 in connection with nozzles for, discharging liquids or gases into' atmosphere sur- When air or other .gas is rounding rotor H, it is to be understood as com ing within the scope, of this invention to employ such nozzlesnot in connection with a casing such as casing 26. While jets or nozzles as shown above may be used according to this invention,

it is to be understood that other members and arrangements of jets or nozzles may be utilized and that other means may be used to discharge or release adjacent the exterior of the rotor a substance adapted to affect the rate of heat flow through the wall of the rotor. Any method of circulating air, other gases or vapors or mixtures thereof (all of which are to be understood as being included in the term atmosphere) about the exterior of the centrifugal rotor (to chill same,- for example) may be employed according to this invention. By any of such methods or apparatus the conditions surrounding the exterior of the centrifugal rotor may be modified so as to con-' trol, according to this invention, the dissipation of heat developed at or adjacentthe rotor wall in subjecting substances to centrifugal treatment and to thereby also control the-temperature of the rotor wall and of substances adjacent the wall in the interior of the rotor.

In Fig. 3 a further embodiment of this invention is shown. The construction is similar to the apparatus shown in Fig. 1, except that a single walled casing 29 may be used and that there is included in the space between casing 29 and rotor H a coil 38 which is adapted to have liquids or gases of desired temperature circulated therethrough. The casing 29 may be provided with suitable openings 38 for inlet and outlet pipes 32 4 connectedto coil 30. While a helical coil is shown, it is to be understood that other devices adapted to have liquids or gases of desired tem-' peratur flow therethrough may be used-accordcontrolled so as to produce heat transfer for example, from rotor M'to coil 36 and maintain the temperature of the wall of rotor ii at a temperas ture favorable to 'substancesdeposited thereon.

While this invention has been described in connection with specific embodiments thereof and specific methods of practising this invention, it is to be understood that this has been done for-purposes of illustration merely. While this invention has been specifically described in connection with .the centrifugal recovery of acidophilus bacilli from culture media in'which they are developed and comprises a great improvement in methods and apparatus heretofore used in connection therewith, it is to be understood that this invention is also applicable inconnection with the centrifugal treatment of other substances which might be deleteriously aifected by the heat developed at or adjacent to the wall of a'centrifugal rotor in subjecting. substances to centrifugaltreatment therein. This invention is especially applicable ing to this invention. According to the above perature such substance.

in the centrifugal treatment of substances in main adjacent to the wall of the rotor for a. substantialperiod of time ,and wherein such substances would be injuriously-afiected' by heat developed at or adjacent to the wall of the centrifugal rotor, were not the heat so developed dissipated as fast as generated in the practice of this invention. p

This invention is also applicable in passing substances through a centrifugalrotor whenever it is desired to maintain the substance thus treated centrifugally within the limits of a narrow temrange, or to prevent parts thereof adjacent the walls of the centrifugal rotor from being subjected to temperatures unfavorable to This invention is alsoapplicable maintaining the temperature of the wall of the centrifugal rotor at a desired temperature with respect to materials subjectedto treatment in the centrifugalrotor or in giving a favorable difference in temperature between the wall of the centrifugal rotor and liquid passing through the rotor with respect to liquids or solids deposited on the wallof the rotor. With respect to the last-named application of this invention, themechanism and methods of this invention may also be employed to maintain the temperature of the centrifugal rotor at a temperature substantially higher than the temperature which the wall of the rotor would attain were the method and apparatus ployed. Furthermore, the temperature of the wall of the rotor may be maintained according to of this invention not em-' the mechanism and method of this invention at temperatures substantially below the temperature of material introduced into the centrifugal rotor in the event that such temperature difier-' ence between the wall of the rotor and the material therein should become desirable.

I claim:

1. The method of separating bacilli from a culture medium which comprises subjecting said medium to centrifugal force in a centrifugal rotor to separate said bacilli from the medium by depositation' of the bacilli against the wall of the rotor, and extracting heat from the rotor wall during such centrifugal treatment at a controlled rate adapted toprevent deleterious effect upon said bacilli of heat generated by said centrifugal treatment.

2'. The method of separating living bacilli from a culture medium which comprises subjecting said medium to centrifugal force in a centrifugal rotor toseparate said bacilli from the medium by depositation of the bacilli against the wall of the rotor, and extracting heat exteriorly from the rotor wall during such centrifugal treatment at a controlled rate adapted to prevent deleterious eflect upon said bacilli of heat generated by said centrifugal treatment.

3. The method of separating living bacilli from a culture medium which comprises subjecting said medium to centrifugal force in a centrifugal rotor to separate said bacilli from the medium by depositation of the bacilli against the wall of the rotor, .and extracting. heat from the substances undercentrifugal treatment at a controlled rate adapted to prevent deleterious effect uponthe deposited bacilli.

LEO D. JONES. 

